This is something I've been hearing recently. This blog also extends to discussions of requests for MSDS (Material Safety Data Sheets) for organic products. First, let's be clear about what an MSDS is: this is an information sheet containing physical and chemical information on a particular substance. It quantifies that substance's risks, safety and impact on the environment. Everyone can use these sheets, although they are mainly designed to provide workers, transporters, and emergency personnel with procedures for handling and working with various substances in a safe manner.
I feel that these arguments are nothing more than a smoke screen intended to confuse people.
Yes, it is true that some organic products are toxic and even dangerous: organic biocides (herbicides and pesticides) are toxic. They have to be, since they are intended to kill something. We must all recognize that everything in our environment is potentially hazardous. "All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy" -- Paracelsus (15th century father of toxicology). If a substance was designed or produced to kill something, it is not likely to be really good for you.
In my mind, the difference between synthetic and organic herbicides and pesticides is that many if not all of the commonly used organic products are based on chemicals that are produced by organisms (like your body). For the most part your body has systems in place to detoxify these because they are not novel agents.
Also, the adverse effects of exposure to these are limited and not a big surprise: boiling water burns, vinegar is an acid, don't get dirt or compost or dust in your eyes and try not to inhale it because it can make you choke. DUH! These effects are far different from synthetic chemicals that can interfere with hormones in your body and result in endocrine disruption or cause DNA damage or hurt your nervous system and brain.
However, such discussions of product safety misses the point entirely. Organic lawn care should emphasize changing cultural practices to make the plants you want to grow more healthy. Organic practices choose the best plant for the situation and provide that plant with what it needs to thrive. Plants that are thriving will generally be less susceptible to disease, insect infestation, or competition from other plants.
To accomplish this you need to understanding what species and strain of plant will do well in your environment and giving it what it needs. Choose your plant species and strain based on what best suits your environment (light conditions, water availability, traffic, etc). In general, healthy soil leads to healthy plants. Start with understanding your current soil condition (what is the pH, nutrient and organic mater levels, etc.? how compacted is it? how wet/dry is it? loamy, sandy, clay?). Then determine how much it will cost (including labor) to get from where you are currently to where you need to be for your plant species/strain to thrive. Based on the resources required, do you want to rethink your plant species/strain?
The most commonly used product on an established organic lawn should be compost and compost tea. During transition and perhaps to deal with an occasional problem, a product may be necessary to address an infestation or issue (e.g., horticultural oil to smother insects). A MSDS for compost tea or compost is a silly request. My vermicompost tea is water, vermicompost, air, and molasses. Do you really expect an MSDS for dilute muddy water to be informative? Don't get it in your eyes and don't drink or breathe it. Wash your hands after use. DUH!
By emphasizing that organic lawn care should emphasize practices to make plants healthy by addressing problems (not products that address signs and symptoms of problems), we can move beyond these discussions.